Expand.
Solution: $\begin{aligned} &\phantom{=}({1-4m})(m^2-3m+8) \\\\ &={1}(m^2-3m+8){-4m}(m^2-3m+8) \end{aligned}$ $\begin{aligned} &=m^2-3m+8-4m^3+12m^2-32m \\\\ &=-4m^3+13m^2-35m+8 \end{aligned}$